(Visual Basic 6.0) Automatically Refresh Token for 401 Unauthorized

Demonstrates how to automatically refresh an access token (without user interaction) when the token expires and a 401 Unauthorized response is received.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim tokenFilePath As String
tokenFilePath = "qa_data/tokens/googleCalendar.json"

' Get our current access token.
Dim jsonToken As New ChilkatJsonObject
Dim success As Long
success = jsonToken.LoadFile(tokenFilePath)
If (jsonToken.HasMember("access_token") = 0) Then
    Debug.Print "No access token found."
    Exit Sub
End If

Dim http As New ChilkatHttp
http.AuthToken = jsonToken.StringOf("access_token")

Dim jsonResponse As String
jsonResponse = http.QuickGetStr("https://www.googleapis.com/calendar/v3/users/me/calendarList")
If (http.LastMethodSuccess <> 1) Then

    If (http.LastStatus <> 401) Then
        Debug.Print http.LastErrorText
        Debug.Print "----"
        Debug.Print http.LastResponseBody
        Exit Sub
    End If

    ' The access token must've expired. 
    ' Refresh the access token and then retry the request.
    Dim oauth2 As New ChilkatOAuth2

    oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

    ' Replace these with actual values.
    oauth2.ClientId = "GOOGLE-CLIENT-ID"
    oauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

    ' Get the "refresh_token"
    oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

    ' Send the HTTP POST to refresh the access token..
    success = oauth2.RefreshAccessToken()
    If (success <> 1) Then
        Debug.Print oauth2.LastErrorText
        Exit Sub
    End If

    ' The response contains a new access token, but we must keep
    ' our existing refresh token for when we need to refresh again in the future.
    success = jsonToken.UpdateString("access_token",oauth2.AccessToken)

    ' Save the new JSON access token response to a file.
    Dim sbJson As New ChilkatStringBuilder
    jsonToken.EmitCompact = 0
    success = jsonToken.EmitSb(sbJson)
    success = sbJson.WriteFile(tokenFilePath,"utf-8",0)

    Debug.Print "OAuth2 authorization granted!"
    Debug.Print "New Access Token = " & oauth2.AccessToken

    ' re-try the original request.
    http.AuthToken = oauth2.AccessToken
    jsonResponse = http.QuickGetStr("https://www.googleapis.com/calendar/v3/users/me/calendarList")
    If (http.LastMethodSuccess <> 1) Then
        Debug.Print http.LastErrorText
        Exit Sub
    End If

End If

Debug.Print jsonResponse
Debug.Print "-----------------------------"